1. Field of the Invention
The present invention relates to an image processing apparatus which detects a character, in particular, large dots, in image data and performs a suitable image processing for the detected image, an image reading apparatus equipped with the image processing apparatus, an image forming apparatus equipped with the image processing apparatus, and a color copier equipped with the image processing apparatus.
2. Description of the Related Art
For example, Japanese Patent No. 2778669 discloses an image processing method that uses the technology of the type as mentioned above. In this image processing method, when detecting a dot in image data, the computation of a peak pixel is performed for the pixels of the image data which are located at predetermined positions.
Moreover, Japanese Laid-Open Patent Application No. 8-149294 discloses an image processing method that is known and is of the above type. In this image processing method, the computation of a peak pixel is performed for the pixels of the image data which are located at predetermined positions by using a plurality of matrices. Japanese Laid-Open Patent Applications No. 8-149289, No. 8-204968 and No. 8-149291 disclose image processing methods that are also known and of the above type. In these image processing methods, the determination of a dot in image data is performed by detecting the periodicity. Furthermore, Japanese Laid-Open Patent Application No. 9-51432 discloses an image processing method which is known and is of the above type. In this image processing method, the determination of a dot is made when a predetermined periodicity difference is small.
However, in each of the above-mentioned conventional methods, when detecting a low-linear-density dot (100 or less lines), the difference between the low-linear-density dot and a small character in the image data becomes very small. It is difficult that each of the conventional methods performs the segmentation of a small character and a dot. Each of the conventional methods does not take into consideration for the segmentation of a small character and a dot in image data when detecting a low-linear-density dot.